Observers have noted that the flight paths of America’s X-37B spacecraft and China’s Tiangong-1 space station are very similar, leading to speculation that the US craft could be being used to spy on China’s project.

Details of the X-37B, which was launched in 2011, are scarce. The craft was originally developed by NASA more than a decade ago, before being taken over by the Defense Advanced Research Projects Agency (DARPA). There’s speculation that the X-37B is being used to test equipment for the National Reconnaissance Office (NRO) intelligence agency.

Some people are sceptical that the X-37B is really shadowing the Chinese space station, pointing out that their flight paths do not match entirely and that if that really were the X-37B’s purpose, it would have better options. Nevertheless, it’s clear that the mystery and intrigue surrounding the X-37B have captured the imagination of many people.